When Paul Rudd tells an embarrassing story, he leaves in details other celebrities might be too proud to reveal.

The 39-year-old actor cringes with amusement as he remembers the time, less than two weeks ago, when he got caught in an awkward situation while promoting his new comedy “I Love You, Man” in Toronto.

Rudd, taking a bathroom break with co-star Jason Segel before a TV interview, thought it’d be funny to pull his drawers down to his ankles.

The joke scored laughs from his one-man audience, recalls Rudd, but backfired when Segel walked out the door and a stranger entered.

“I’m pulling my pants up in front of a urinal and my (rear end) is sticking out and the guy just like, walks in,” Rudd said during in a recent interview.

He tried to explain, but it was no use. According to Segel, said Rudd, the unwitting bystander “walked to his friend, kind of shaken, and said ‘You won’t believe what I just saw.'”

He says things like that happen to him all the time — which comes as no surprise, given Rudd’s special knack for spinning awkward moments into comedy gold.

Rudd serves up massive doses of that awkwardness — and likability — in his latest role as an insecure, squarish real estate agent in “I Love You, Man,” directed by John Hamburg, which opens Friday.

Rudd’s character, Peter, has always focused on a girlfriend, at the expense of male friendships, and has no close friends to be best man at his wedding. So he embarks on some failed man dates to find Mr. Right, eventually clicking with easygoing bachelor Sydney (Segel), who shows up at an open house for the free food and lusty divorcees.

Peter tries to impress Sydney, making jokes that fall flat (he randomly calls his new pal “Jobin” in a futile effort to banter like a bro).

“I know that feeling of insecurity and overcompensation that I try to do with the character but I don’t think I’m quite as awkward as some of those moments,” said Rudd, adding: “But I can be.”

Donald De Line, who produced the film, calls Rudd an authentic fit.

“He has that incredibly likable, open, sweet quality — kind of that Everyman quality — and at the same time, he just a little bit throws you off kilter,” said De Line.

Rudd regularly appears in the films of Hollywood comedy mogul Judd Apatow, whose world is populated by geeky guys: The actor walked the line between stalkery and sweetheart as a sad-sack electronics store employee pining for his ex in “The 40-Year-Old Virgin.” He played a put-upon husband in “Knocked Up” and an absent-minded surfer in “Forgetting Sarah Marshall.”

“I imagine I just play average guys who — whatever they’re going through — are relatable,” Rudd said of his various alter egos. “That’s what’s interesting to me. I don’t think I’d be a very good action guy.”

Rudd, who lives in Manhattan with his wife, Julie, and 3-year-old son, is engaging and friendly during an interview, free-associating about the April issue of Vanity Fair declaring him a “new legend” of comedy (he jokes the true comic legends are Paul Bunyan, Johnny Appleseed and Bagger Vance) and the term “bromance” (which he hopes “will die an ugly and painful death”).

Not that he’s ever had an issue with finding pals.

“My mother always said that I was good at making friends,” he said, “and that I never had a friend that she would not adopt as her own son.”